US12140739B2ActiveUtilityA1

Zoom optical system, optical apparatus and method for manufacturing the zoom optical system

Assignee: NIKON CORPPriority: Jun 14, 2019Filed: May 27, 2020Granted: Nov 12, 2024

Est. expiryJun 14, 2039(~12.9 yrs left)· nominal 20-yr term from priority

Inventors:Kosuke Machida

G02B 15/20G02B 15/1425G02B 15/22G02B 15/1421G02B 13/18G02B 15/16G02B 15/1461G02B 7/10

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References

Claims

Abstract

A variable power optical system (ZL ( 1 )) includes a plurality of lens groups (G 1 -G 7 ). During variable magnification, an interval between adjacent lens groups changes. The plurality of lens groups include: a first focusing lens group (G 5 ) that moves during focusing; and a second focusing lens group (G 6 ) that is disposed more toward an imaging surface side than the first focusing lens group and that moves along a different trajectory than the first focusing lens group during focusing. The first focusing lens group and the second focusing lens group both have a negative refractive power. The plurality of lens groups satisfy the following condition: 0.40<fF1/fF2<3.50 (wherein fF1 is the focal distance of the first focusing lens group, and fF2 is the focal distance of the second focusing lens group).

Claims

exact text as granted — not AI-modified

The invention claimed is: 
     
       1. A zoom optical system comprising a plurality of lens groups, wherein
 distances between adjacent lens groups among the plurality of lens groups change upon zooming, 
 the plurality of lens groups include: a first focusing lens group that moves upon focusing; and a second focusing lens group that is disposed closer to an image surface than the first focusing lens group, and moves on a trajectory different from a trajectory of the first focusing lens group upon focusing, 
 the first focusing lens group and the second focusing lens group each have a negative refractive power, and 
 the following conditional expressions are satisfied:
   0.40&lt; fF 1 /fF 2&lt;3.50 
   (β WF 1+1/β WF 1) −2 &lt;0.250
 
 
 where 
 fF1: a focal length of the first focusing lens group, 
 fF2: a focal length of the second focusing lens group, and 
 βWF1: a lateral magnification of the first focusing lens group upon focusing on an infinity object in a wide angle end state. 
 
     
     
       2. The zoom optical system according to  claim 1 , wherein
 the following conditional expression is satisfied:
   0.20&lt;(− fFs )/ ft &lt;2.00
 
 
 fFs: a focal length of either the first focusing lens group or the second focusing lens group which has a stronger refractive power than the other, and 
 ft: a focal length of the zoom optical system in a telephoto end state. 
 
     
     
       3. The zoom optical system according to  claim 1 , wherein the first focusing lens group moves in a direction toward the image surface upon focusing from an infinity object to a short distant object. 
     
     
       4. The zoom optical system according to  claim 1 , wherein the second focusing lens group moves in a direction toward the image surface upon focusing from an infinity object to a short distant object. 
     
     
       5. The zoom optical system according to  claim 1 , wherein
 the following conditional expression is satisfied:
   1.00&lt;(− fFs )/ fw&lt; 4.00
 
 
 where 
 fFs: a focal length of either the first focusing lens group or the second focusing lens group which has a stronger refractive power than the other, and 
 fw: a focal length of the zoom optical system in a wide angle end state. 
 
     
     
       6. The zoom optical system according to  claim 1 , wherein
 the following conditional expression is satisfied:
   0.10&lt; MWF 1/ MWF 2&lt;3.00 
 
 where 
 MWF1: an absolute value of an amount of movement of the first focusing lens group upon focusing from an infinity object to a short distant object in a wide angle end state, and 
 MWF2: an absolute value of an amount of movement of the second focusing lens group upon focusing from the infinity object to the short distant object in the wide angle end state. 
 
     
     
       7. The zoom optical system according to  claim 1 , wherein
 the following conditional expression is satisfied:
   0.20&lt; βWF 1/ βWF 2&lt;5.00 
 
 where 
 βWF1: a lateral magnification of the first focusing lens group upon focusing on an infinity object in a wide angle end state, and 
 βWF2: a lateral magnification of the second focusing lens group upon focusing on the infinity object in the wide angle end state. 
 
     
     
       8. The zoom optical system according to  claim 1 , wherein the plurality of lens groups include a succeeding lens group disposed closer to the image surface than the second focusing lens group, and the succeeding lens group consists of at least one lens group. 
     
     
       9. The zoom optical system according to  claim 1 , wherein the plurality of lens groups include a succeeding lens group disposed closer to the image surface than the second focusing lens group, and
 the following conditional expression is satisfied:
   −2.00&lt;(− fFs )/ fR&lt; 2.00
 
 
 where 
 fFs: a focal length of either the first focusing lens group or the second focusing lens group which has a stronger refractive power than the other, and 
 fR: a focal length of the succeeding lens group. 
 
     
     
       10. The zoom optical system according to  claim 1 , wherein the plurality of lens groups include a preceding lens group disposed closer to an object than the first focusing lens group, and the preceding lens group consists of at least one lens group. 
     
     
       11. The zoom optical system according to  claim 1 , wherein the plurality of lens groups include a preceding lens group disposed closer to an object than the first focusing lens group, and
 the following conditional expression is satisfied:
   0.30&lt;(− fFs )/ fF&lt; 3.00
 
 
 where 
 fFs: a focal length of either the first focusing lens group or the second focusing lens group which has a stronger refractive power than the other, and 
 fF: a focal length of a lens group adjacent to the first focusing lens group among lens groups consisting of the preceding lens group. 
 
     
     
       12. The zoom optical system according to  claim 1 , wherein the plurality of lens groups include a preceding lens group disposed closer to an object than the first focusing lens group, and
 the preceding lens group includes a first lens group that has a positive refractive power and is disposed closest to an object. 
 
     
     
       13. The zoom optical system according to  claim 1 , wherein the plurality of lens groups include a preceding lens group disposed closer to an object than the first focusing lens group,
 the preceding lens group includes: a first lens group that has a positive refractive power and is disposed closest to the object; and a second lens group that has a negative refractive power and is disposed adjacent to an image surface of the first lens group, and 
 the first focusing lens group is disposed closest to the object among all the focusing lens groups. 
 
     
     
       14. The zoom optical system according to  claim 1 , wherein the plurality of lens groups include, in order closest from an object: a first lens group having a positive refractive power; and a second lens group having a negative refractive power, and
 the following conditional expression is satisfied:
   4.00&lt; f 1/(− f 2)&lt;8.00
 
 
 where 
 f1: a focal length of the first lens group, and 
 f2: a focal length of the second lens group. 
 
     
     
       15. The zoom optical system according to  claim 1 , wherein
 the following conditional expression is satisfied:
   2ω w&gt; 75.0°
 
 
 where 
 ωw: a half angle of view of the zoom optical system in a wide angle end state. 
 
     
     
       16. The zoom optical system according to  claim 1 , wherein
 the following conditional expression is satisfied:
   0.10&lt; BFw/fw&lt; 1.00 
 
 where 
 BFw: a back focus of the zoom optical system in a wide-angle end state, and 
 fw: a focal length of the zoom optical system in the wide angle end state. 
 
     
     
       17. The zoom optical system according to  claim 1 , wherein
 the second focusing lens group has a lens component having a negative refractive power, and the lens component satisfies the following conditional expression:
   −2.00&lt;( r 2+ r 1)/( r 2− r 1)&lt;6.00
 
 
 where 
 r1: a radius of curvature of a lens surface of the lens component on an object side, and 
 r2: a radius of curvature of a lens surface of the lens component on an image side. 
 
     
     
       18. The zoom optical system according to  claim 1 , wherein
 the following conditional expression is satisfied:
   1.05&lt;β WF 1&lt;1.80
 
 
 where 
 βWF1: a lateral magnification of the first focusing lens group upon focusing on an infinity object in a wide angle end state. 
 
     
     
       19. The zoom optical system according to  claim 1 , wherein
 the following conditional expression is satisfied:
   1.05&lt;β WF 2&lt;1.80
 
 
 where 
 βWF2: a lateral magnification of the second focusing lens group upon focusing on an infinity object in a wide angle end state. 
 
     
     
       20. The zoom optical system according to  claim 1 , wherein
 the following conditional expression is satisfied:
   (β WF 2+1/β WF 2) −2 &lt;0.250
 
 
 where 
 βWF2: a lateral magnification of the second focusing lens group upon focusing on an infinity object in a wide angle end state. 
 
     
     
       21. An optical apparatus mounted with the zoom optical system according to  claim 1 . 
     
     
       22. A method for manufacturing a zoom optical system comprising a plurality of lens groups, wherein
 distances between adjacent lens groups among the plurality of lens groups change upon zooming, 
 the plurality of lens groups include: a first focusing lens group that moves upon focusing; and a second focusing lens group that is disposed closer to an image surface than the first focusing lens group, and moves on a trajectory different from a trajectory of the first focusing lens group upon focusing, 
 the first focusing lens group and the second focusing lens group each have a negative refractive power, and 
 the method configures each of the lens groups and arranges the groups in a lens barrel so as to satisfy the following conditional expressions:
   0.40&lt; fF 1/ fF 2&lt;3.50 
   (β WF 1+1/β WF 1) −2 &lt;0.250
 
 
 where 
 fF1: a focal length of the first focusing lens group, 
 fF2: a focal length of the second focusing lens group, and 
 βWF1: a lateral magnification of the first focusing lens group upon focusing on an infinity object in a wide angle end state.

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